optical endstop in parallel to 1 endstop input

tekstyle

Hello there,

I want to connect more than 1 optical endstop together on the E1 enstop input on my duet2wifi. right now if just 1 is connected, the LED on the board stays on by default and turns off when triggered. The way I plan to have it work is optics will be blocked by default. when either of the flags becomes unblocked, I need the duet2wifi to do some basic commands.

I am assuming that the LED will be turned off which the board recognizes as triggered. Therefore, I believe I will need to invert it to Active LOW in config.g
the signal wire on both endstops will be connected. when one goes "untriggered", it will want to send a signal to both the duet2 and also to the other endstop. would this affect how the board senses the signal?

would it be necessary to add diodes with (the arrow pointing towards E1endstop on the board) to further isolate the 2 endstops so they don't interfere with each other?

Thanks in advance.

fcwilt

@tekstyle

Well you will have to rely on the sensor pulling the input low and use a signal diode from the input to each sensor - anode to input.

And enable the input pull-up resistor.

Frederick

dc42

@tekstyle if the sensors use simple slotted opto switches without a separate comparator chip, then you can connect the outputs of the two switches in parallel. The output will be low when either or both are not blocked, high when both are blocked.

tekstyle

@dc42
h**ps://www.amazon.com/DAOKI-Measuring-Optocoupler-Interrupter-Detection/dp/B081W4KMHC/ref=sr_1_3?dchild=1&keywords=arduino+speed+sensor&qid=1626515939&sr=8-3

these are the sensors I have. I believe what I need is it to be high when either one are unblocked and low when both are blocked. basically the reverse. is this even possible?

tekstyle

@fcwilt

i tried placing the diode with anode end towards input. the input pin shows 3V all the time.
i tried placing the diode with cathode end towards the input. It has the same behavior as if there was no diode. all sensors blocked vs just 1 sensor blocked yields the same e1endstop status.

dc42

@tekstyle said in optical endstop in parallel to 1 endstop input:

@dc42
h**ps://www.amazon.com/DAOKI-Measuring-Optocoupler-Interrupter-Detection/dp/B081W4KMHC/ref=sr_1_3?dchild=1&keywords=arduino+speed+sensor&qid=1626515939&sr=8-3

these are the sensors I have. I believe what I need is it to be high when either one are unblocked and low when both are blocked. basically the reverse. is this even possible?

To achieve that I suggest you use one of the four gates in a 74HC02 to OR the two outputs together. It will also invert the output.

fcwilt

@tekstyle

What about when no sensors are blocked.

With the cathode connected to the input some combination of blocked/unblocked should have been different.

Or do as @dc42 suggests and add a part.

tekstyle

@dc42

thats is a great solution. would it be possible to use this IC if i use 3 opto sensors? according to my searches, the 74hC02 is a NOR gate IC.

looking at the truth table, if both input are LOW, the output is HIGH. i am not sure if i can connect the outputs of multiple gates together if i use more than one.

thankd in advance! i think we are getting a little closer

update:
i found a truth table for a OR gate
A | B | X
0 | 0 | 0
1| 0 | 1
0| 1 | 1
1| 1 | 1

this type of IC might work i think but i dont know the model number to search for.

update:
M74HC4075. this uses triple input OR gate. low output when all inputs are low and high on any other condition. would this be a solution?

tekstyle

@fcwilt when no sensors are blocked, the e1 status will change. i need the change to happen when any 1 of 3 sensors becomes unblocked.

this is for a delta arm parallel sensor setup. hence the reason for 3 sensors. i need it to pause print when any one of the sensors trip (block to unblocked)

dc42

@tekstyle 74HC27 is a triple 3-input NOR gate.

tekstyle

@dc42 perfect. thanks david. will get back with updates once it has arrived!

tekstyle

@tekstyle

I got the IC hooked up, and everything is working GREAT! thank you! This is actually a triple 3input OR gate. I just inverted the 1 and 0 in duet firmware.